Selective Precipitation Separation and Inductively Coupled Plasma Mass Spectrometric Determination of Trace Metal Impurities in High Purity Silver
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Yuh-Chang Sun, Jerzy Mierzwa, Chien-Feng Lin, T. I. Yeh and Mo-Hsiung Yang
Abstract
A simple and rapid method for the determination of some trace element impurities in high purity silver, combining the isolation of analytes from the silver matrix with selective precipitation followed by ICP-MS determination was developed. On the basis of an extreme difference in the solubilities of the chlorides of silver and the other accompanying trace elements, silver can be separated completely through the addition of hydrochloric acid. The sample of silver was at first dissolved in 7 M nitric acid followed by addition of hydrochloric acid to remove the silver matrix by formation of a silver chloride precipitate, while leaving the trace element impurities in the solution, which was subsequently analysed by ICP-MS. Eleven elements (Al, Au, Cd, Co, Cu, Fe, Mg, Mn, Ni, Pb and Sn) were determined with good accuracy and precision. The limits of detection (based on the 3ς criterion) of these elements were 10-1–10-3 ng g-1. The proposed method was successfully applied to the determination of metal impurities in high-purity silver samples (EM9465 and EM 9343) and validated by the analysis of NIST SRM 8171 (Fine Silver FS 14).